package com.bang.study.nio.socket;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.time.LocalDateTime;
import java.util.Date;
import java.util.Iterator;
import java.util.Scanner;
import java.util.Set;

import org.junit.Test;

/*
 * 一、使用 NIO 完成网络通信的三个核心：
 *
 * 1. 通道（Channel）：负责连接
 *
 * 	   java.nio.channels.Channel 接口：
 * 			|--SelectableChannel
 * 				|--SocketChannel
 * 				|--ServerSocketChannel
 * 				|--DatagramChannel
 *
 * 				|--Pipe.SinkChannel
 * 				|--Pipe.SourceChannel
 *
 * 2. 缓冲区（Buffer）：负责数据的存取
 *
 * 3. 选择器（Selector）：是 SelectableChannel 的多路复用器。用于监控 SelectableChannel 的 IO 状况
 *
 */
public class TestNonBlockingNIO {

    //客户端
    @Test
    public void client() throws IOException {
        //1. 获取通道
        SocketChannel socketChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 19999));

        //2. 切换非阻塞模式
        socketChannel.configureBlocking(false);

        //3. 分配指定大小的缓冲区
        ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
        System.out.println("请输入:");

        //4. 发送数据给服务端
        Scanner scanner = new Scanner(System.in);

        if (scanner.hasNext()) {
            String next = scanner.next();
            byteBuffer.put((LocalDateTime.now().toString() + "\r\n" + next).getBytes());
            byteBuffer.flip();
            socketChannel.write(byteBuffer);
            byteBuffer.clear();
        }

        //5. 关闭通道
        socketChannel.close();
    }

    //服务端
    @Test
    public void server() throws IOException {
        //1. 获取通道
        ServerSocketChannel ssChannel = ServerSocketChannel.open();

        //2. 切换非阻塞模式
        ssChannel.configureBlocking(false);
        //3. 绑定连接
        ssChannel.bind(new InetSocketAddress(19999));
        //4. 获取选择器
        Selector selector = Selector.open();
        //5. 将通道注册到选择器上, 并且指定“监听接收事件”
        ssChannel.register(selector, SelectionKey.OP_ACCEPT);
        //6. 轮询式的获取选择器上已经“准备就绪”的事件
        while (selector.select() > 0) {
            //7. 获取当前选择器中所有注册的“选择键(已就绪的监听事件)”
            Iterator<SelectionKey> keyIterator = selector.selectedKeys().iterator();
            while (keyIterator.hasNext()) {
                //8. 获取准备“就绪”的是事件
                SelectionKey sk = keyIterator.next();
                //9. 判断具体是什么事件准备就绪
                if (sk.isAcceptable()) {
                    //10. 若“接收就绪”，获取客户端连接
                    SocketChannel sChannel = ssChannel.accept();

                    //11. 切换非阻塞模式
                    sChannel.configureBlocking(false);

                    //12. 将该通道注册到选择器上
                    sChannel.register(selector, SelectionKey.OP_READ);
                } else if (sk.isReadable()) {
                    //13. 获取当前选择器上“读就绪”状态的通道
                    SocketChannel sChannel = (SocketChannel) sk.channel();
                    //14. 读取数据
                    ByteBuffer buffer = ByteBuffer.allocate(1024);
                    int len = 0;
                    while ((len = sChannel.read(buffer)) != -1) {
                        buffer.flip();
                        System.out.println(new String(buffer.array(), 0, len));
                        buffer.clear();
                    }
                }
                //15. 取消选择键 SelectionKey
                keyIterator.remove();
            }
        }


    }


    public static void main(String[] args) throws IOException {
        new TestNonBlockingNIO().client();
    }
}
